Compositions and methods for reducing nitrogen volatilization of urea fertilizers

ABSTRACT

A nitrogen stabilizing composition is provided. The composition includes 10% to 18% w/w N-(n-butyl) thiophosphoric triamide (NBPT), a light oil, an emulsifier, and a solvent including N-methyl-2-pyrrolidone (NMP) and two or more of propylene glycol, ethylene glycol, morpholine and glycerine.

FIELD OF THE INVENTION

This invention relates to compositions and methods for reducing nitrogenvolatilization of urea fertilizers used in agriculture.

BACKGROUND

Urea fertilizer is commonly used as a source of nitrogen in agriculture.Urea is degraded by the enzyme urease, an enzyme that is ubiquitous inagricultural systems. Urease degradation of urea results in the loss ofnitrogen from soil as ammonia in a process called volatilization.Different approaches have been implemented to prevent nitrogen loss fromvolatilization, including the use of the urease inhibitor N-(n-butyl)thiophosphoric triamide (NBPT). Liquid formulations containing NBPT foruse in reducing nitrogen volatilization comprise are known, and forexample are sold under the trademarks AGROTAIN™ and ARBORITE™. Efficientand cost-effective compositions and methods for reducing nitrogenvolatilization of urea fertilizers are desirable.

SUMMARY

The invention described herein has many aspects.

One aspect provides a nitrogen stabilizing composition comprising: 10%to 18% w/w N-(n-butyl) thiophosphoric triamide (NBPT); a solvent; alight oil; and an emulsifier.

The composition may comprise 1% to 5% w/w of the light oil, and thelight oil may be vegetable oil.

The composition may comprise 1% to 5% w/w of the emulsifier, and theemulsifier may be sunflower lecithin.

The composition may comprise 1% to 5% w/w of a surfactant, and thesurfactant may be polysorbate 20.

The solvent may comprise N-methyl-2-pyrrolidone (NMP) combined with anytwo or more of propylene glycol, ethylene glycol, morpholine andglycerine. The composition may comprise 5% to 30% w/w of the NMP, 5% to30% w/w of the propylene glycol, 5% to 30% w/w of the ethylene glycol,2% to 40% w/w of morpholine and 2% to 40% w/w of glycerine.

The composition may be water-free.

The pH of the composition may be pH 6.5 to 7.5.

The composition may comprise 10% to 15% NBPT.

The composition may be provided in a ready-to-use form or a concentratedform. The concentrated form may be selected from the group consisting ofa liquid, gel, and reconstitutable powder.

The composition may be coated with a urea fertilizer to produce a coatedurea fertilizer mixture. The urea fertilizer may be granular or inaqueous solution. The aqueous solution may be a urea-ammonium nitrate(UAN) solution (28-0-0).

The composition may be applied to the urea fertilizer at a rate in arange of approximately 1 L/1000 kg to 10 L/1000 kg. In some embodiments,the composition may be applied to the urea fertilizer at a rate in arange of approximately 1 L/1000 kg to 5 L/1000 kg. In some embodiments,the composition may be applied to the urea fertilizer at a rate in arange of approximately 2 L/1000 kg to 3 L/1000 kg.

Another aspect provides a method for making a liquid nitrogenstabilizing composition comprising:

-   -   (a) dissolving N-(n-butyl) thiophosphoric triamide (NBPT) in a        solvent comprising N-methyl-2-pyrrolidone (NMP) and two or more        of propylene glycol, ethylene glycol, morpholine and glycerine;        and    -   (b) adding a vegetable oil and an emulsifier to the mixture from        step (a),    -   wherein final concentrations of components in the composition        are:    -   10% to 15% w/w NBPT;    -   1% to 5% w/w vegetable oil; and    -   1% to 5% w/w emulsifier.

The vegetable oil may be canola oil. The emulsifier may be sunflowerlecithin.

The method may further comprise:

-   -   (c) adding a surfactant to the mixture of step (b), wherein a        final concentration of the surfactant is 1% to 5% w/w.

The surfactant may be polysorbate 20.

Another aspect provides a method of making a coated urea fertilizercomprising:

-   -   (a) making a liquid nitrogen stabilizing composition according        to the method of claim 11;    -   (b) blending the composition with urea granules at a ratio of 1        L/1000 kg to 3 L/1000 kg.

The method may comprise:

-   -   (c) adding an additional fertilizer to the mixture of step (b),        wherein the additional fertilizer comprises phosphorus,        potassium and/or sulfur.

Another aspect provides a method of fertilizing soil comprising applyingto the soil to be fertilized a coated urea fertilizer according to theinvention. The coated urea fertilizer may be applied at a rate of 50 to500 pounds per acre, or 100 to 150 pounds per acre.

Another aspect provides a method of making a liquid urea fertilizersolution comprising:

-   -   (a) making a liquid nitrogen stabilizing composition according        to the method of claim 13;    -   (b) mixing the composition with a urea-ammonium nitrate (UAN)        solution, or an ammonium-polyphosphate (APP) solution at a ratio        of 0.5 L/1000 L to 3.0 L/1000 L.

Another aspect provides a method of fertilizing soil comprising applyingto the soil to be fertilized a liquid urea fertilizer according to theinvention. The liquid urea fertilizer may be applied at a rate of 0.5 Lto 1.5 L/acre or about 1 L/acre.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings illustrate non-limiting example embodiments ofthe invention.

FIG. 1A is a table showing the effects on ammonia emissions of coatedurea containing a composition according to an embodiment and two knowncommercial compositions at 24, 48, 72, 96 and 120 hours after treatment.FIG. 1B is a table comparing the effects on ammonia emissions of coatedurea containing a composition according to an embodiment and coated ureacontaining the known commercial composition AGROTAIN™ at 24, 48, 72, 96and 120 hours after treatment, with results showing in the form ofratios, expressed as percentages. FIG. 1C is a table comparing theeffects on ammonia emissions of coated urea containing a compositionaccording to an embodiment and coated urea containing the knowncommercial composition ARBORITE™ at 24, 48, 72, 96 and 120 hours aftertreatment, with results showing in the form of ratios, expressed aspercentages.

FIGS. 2A to 2C are graphs showing ammonia emissions of urea granulestreated with a composition according to an embodiment at: 24 hours aftertreatment in FIG. 2A, 48 hours after treatment in FIG. 2B, and 72 hoursafter treatment in FIG. 2C.

FIG. 3A is a graph showing the effects on ammonia emissions of coatedurea that is mixed with topsoil containing a composition according to anembodiment and two known commercial compositions at 24, 48, 72 hours and7 days after treatment. FIG. 3B is a graph showing same at 14, 21 and 28days after treatment. FIG. 3C is a table showing the data of FIG. 3B intabular form.

FIG. 4A is a table showing the effects on ammonia emissions of coatedurea-ammonium nitrate (UAN) solution (28-0-0) containing a compositionaccording to an embodiment and two known commercial compositions at 1,2, 5, 7 and 10 days after treatment. FIG. 4B is a graph showing the dataof FIG. 4A in graphic form.

FIG. 5A is a photograph of a composition according to an embodiment ofinvention. FIG. 5B is a photograph of the composition being added tourea granules on a moving belt. FIG. 5C is a photograph of the ureagranules and the composition being blended in a screw mixer. FIG. 5D isa photograph of the urea granules coated with the composition. FIG. 5Eis a photograph of the coated urea granules blended with additionalfertilizer granules. FIG. 5F is a photograph of a transfer auger afterbeing used to transfer the coated urea granules. FIGS. 5G to 5I arephotographs of a component of the applicator machinery: FIG. 5G showsthe component before any coverage with the blended fertilizer granules,FIG. 5H shows the component after coverage of 100 acres with the blendedfertilizer granules, and FIG. 5I shows the component after coverage of200 acres with the blended fertilizer granules.

FIG. 6A is a graph showing daily ammonia emissions from uncoatedurea-based fertilizer, urea-based fertilizer coated with 2 L/1000 kg and3 L/1000 kg of a composition according to an embodiment, and urea-basedcoated fertilizer containing two commercial compositions uponapplication to soil surface measured over 28 days. FIG. 6B is a tableshowing cumulative ammonia volatilization losses measured over 28 days.FIG. 6C is a graph comparing the effects of coated urea-based fertilizerand uncoated urea-based fertilizer at 28 days after fertilization, withresults showing in the form of ratios, expressed as percentages.

DETAILED DESCRIPTION

Throughout the following description, specific details are set forth inorder to provide a more thorough understanding to persons skilled in theart. However, well known elements may not have been shown or describedin detail to avoid unnecessarily obscuring the disclosure. Accordingly,the description and drawings are to be regarded in an illustrative,rather than a restrictive, sense.

As used herein, a value % w/w means the weight percent of a component ofthe composition with respect to the total weight of said composition.

Known liquid formulations of NBPT for use in reducing nitrogenvolatilization such as those commercially available under the trademarksAGROTAIN™ and ARBORITE™ comprise approximately 24% of NBPT by totalweight of solution. Since NBPT is a solid compound, coating NBPT ontourea requires NBPT to be introduced into a liquid carrier prior to beingmixed with urea. Accordingly, the greater the amount of NBPT used in aparticular formulation, the greater amount of solvent required, and bothfactors increase costs.

The inventor has determined that NBPT in known liquid formulations suchas the AGROTAIN™ and ARBORITE™ formulations precipitates at roomtemperature over time. The inventor has also determined that knownliquid formulations of NBPT such as the AGROTAIN™ and ARBORITE™formulations form undesirable dust particulates comprising NBPT. Theinventor has further determined that the dust particulates (i) adhereand cake to components of the mixing machinery during blending of theformulations with urea to coat the urea, as well as to components of theapplicator machinery during application of the coated urea to soil,thereby reducing the availability of NBPT for coating and inhibitingeven coating of the urea.

One aspect relates to an oil-based liquid nitrogen stabilizingcomposition comprising 10% to 18% w/w of NBPT, a solvent, a light oiland an emulsifier. In some embodiments the composition comprises 10% to15% NBPT. Light oils include vegetable oils, essential oils, lightmineral oils, light animal oils and similar substances. Light oils canbe contrasted to heavy oils, which include lubricating oils, fuel oil,gas oil, kerosene and similar substances. In some embodiments thecomposition is free of any heavy oils. In some embodiments the light oilmay be a vegetable oil. In some embodiments, vegetable oil may be theonly oil in the composition.

In some embodiments, the vegetable oil and emulsifier each make up 1% to5% w/w of the composition. In some embodiments the composition may alsocomprise 1% to 5% w/w of a surfactant. In some embodiments, the pH ofthe composition is pH 6.5 to pH 7.5. In some embodiments, the pH of thecomposition is less than pH 7. In some embodiments the composition mayinclude water, a colouring agent and/or a stabilizer. In someembodiments, the composition is water-free.

In some embodiments, the solvent may, for example, be selected from oneor more of a pyrrolidone (e.g. N-methyl pyrrolidone (NMP)), an alkyleneor polyalkylene glycol (e.g. ethylene glycol, propylene glycol, andbutylene glycol), morpholine, glycerine, dimethyl sulfoxide, analkanolamine (e.g. ethanolamine, diethanolamine, dipropanolamine, methyldiethanolamine, monoisopropanolamine and triethanolamine) and/or analkyl lactate (e.g. ethyl lactate, propyl lactate, and butyl lactate).In some embodiments the solvent is a combination of NMP and any two ormore of propylene glycol, ethylene glycol, morpholine and glycerine. Insome embodiments the solvent is a combination of 5% to 30% w/w of theNMP, 5% to 30% w/w of the propylene glycol and 5% to 30% w/w of theethylene glycol. In some embodiments the solvent is a combination of 30%to 40% w/w of the NMP, and 2% to 40% w/w of morpholine and/or 2% to 40%w/w of glycerine.

In some embodiments, the emulsifiers may, for example, be selected fromone or more of monoglycerides, diglycerides, acetylated monoglycerides,sorbitan trioleate, glycerol dioleate, sorbitan tristearate,propyleneglycol monostearate, glycerol monooleate and monostearate,sorbitan monooleate, propylene glycol monolaurate, sorbitanmonostearate, sodium stearoyl lactylate, calcium stearoyl lactylate,glycerol sorbitan monopalmitate, diacetylated tartaric acid esters ofmonoglycerides, lecithins, lysolecithins, succinic acid esters of mono-and/or diglycerides, lactic acid esters of mono- and/or diglycerides,lecithins, lysolecitins, and sucrose esters of fatty acids, lecithin(e.g. soy lecithin, canola lecithin, sunflower lecithin, and/orsafflower lecithin), and lysolecithins. In some embodiments theemulsifier is sunflower lecithin, a product that is commerciallyavailable under the trademark TOPCITHIN™.

In some embodiments, the surfactant may, for example, be selected fromone or more of polysorbate 20 (TWEEN™ 20), polysorbate 40 (TWEEN™ 40),polysorbate 60 (TWEEN™ 60) and polysorbate 80 (TWEEN™ 80). In someembodiments the surfactant is polysorbate 20 (TWEEN™ 20).

In some embodiments, the vegetable oils may, for example, be selectedfrom one or more of canola oil, corn oil, rapeseed oil, cottonseed oil,soybean oil and sunflower oil. In some embodiments the vegetable oil iscanola oil.

In some embodiments, the stabilizers may, for example, be selected fromone or more of xanthan gum, carageenan, maltodextrin, pectin, inulin,starch, gelatin and agar. In some embodiments the stabilizer is xanthangum.

In some embodiments, the colouring agent may, for example, be selectedfrom blue, purple and green dyes. In some embodiments the colouringagent is a blue dye.

In some embodiments, the compositions described herein can be providedin concentrate form (e.g., liquid, gel, or reconstitutable powder form),suitable for further dilution and/or mixing in water or other suitablediluent prior to application. In some embodiments, the compositionsdisclosed and described herein can be provided as a ready-to-usesolution for direct application. In some embodiments, the compositionsdescribed herein can be combined with other fertilizer solutions, andthus are formulated to be diluted and/or reconstituted by mixing withsuch other solutions.

Unexpected and surprising properties of the compositions of the presentinvention compared to commercially available formulations such asAGROTAIN™ and ARBORITE™ include: (i) inhibition of dust formation,resulting in less caking on mixing machinery and applicator machineryand greater availability of NBPT; (ii) NBPT staying in solutionindefinitely; (iii) lower viscosity, allowing enhanced and evenspreading of the resulting liquid composition on urea; (iv) lowerfreezing point, allowing use and easier handling in winter conditions;and (v) less adherence to metal components of the mixing machinery andapplicator machinery.

Another aspect relates to methods for making a liquid nitrogenstabilizing composition. In some embodiments the method includesdissolving N-(n-butyl) thiophosphoric triamide (NBPT) in a solventcomprising N-methyl-2-pyrrolidone (NMP), and two or more of propyleneglycol, ethylene glycol, morpholine and glycerine followed by adding avegetable oil and an emulsifier to the mixture of NBPT and solvents. Insome embodiments the final concentrations of components in thecomposition are 10% to 15% w/w NBPT, 1% to 5% w/w vegetable oil, and 1%to 5% w/w emulsifier. In some embodiments the vegetable oil is canolaoil. In some embodiments the emulsifier is sunflower lecithin. In someembodiments the method includes adding surfactant to the mixture ofNBPT, solvents, vegetable oil and emulsifier. In some embodiments thefinal concentration of the surfactant is 1% to 5% w/w. In someembodiments the surfactant is polysorbate 20.

Another aspect relates to methods for making a coated urea fertilizer.In some embodiments the method includes making a liquid nitrogenstabilizing composition as described herein, followed by blending thecomposition with urea granules at a ratio of 1 L/1000 kg to 3 L/1000 kg.In some embodiments, the additional fertilizer may be added to themixture of the composition and urea granules. In some embodiments, theadditional fertilizer may be added to the composition before blendingwith the urea granules. In some embodiments, the additional fertilizermay include a source of phosphorus, potassium and/or sulfur.

Another aspect relates to methods for fertilizing soil. In someembodiments the method includes applying to soil to be fertilized acoated urea fertilizer as described herein. In some embodiments theapplication rate of the coated urea fertilizer may be 50 to 500 poundsper acre, or 100 to 150 pounds per acre.

Another aspect relates to methods for making a liquid urea fertilizersolution. In some embodiments the method includes making a liquidnitrogen stabilizing composition as described herein, followed by mixingthe composition with a urea-ammonium nitrate (UAN) solution, or anammonium-polyphosphate (APP) solution at a ratio range of 0.5 L/1000 Lto 3.0 L/1000 L, or 1.0 L/1000 L to 1.5 L/1000 L. UAN solutionscontaining 28%, 30% and 32% of nitrogen are commercially available andother customized concentrations and formulations can be obtained.Ammonium-polyphosphate solutions containing about 34% to about 37%phosphorus pentoxide are commercially available, and other customizedconcentrations and formulations can be obtained.

Another aspect relates to methods for fertilizing soil. In someembodiments the method includes applying to soil to be fertilized aliquid urea fertilizer solution as described herein. In some embodimentsthe application rate may be 0.5 to 1.5 L/acre, or about 1 L/acre.

This application is intended to cover any variations, uses, oradaptations of the invention using its general principles. Further, thisapplication is intended to cover such departures from the presentdisclosures as come within known or customary practice in the art towhich this invention pertains and which fall within the limits of theappended claims. Accordingly, the scope of the claims should not belimited by the preferred embodiments set forth in the description, butshould be given the broadest interpretation consistent with thedescription as a whole.

Examples

The invention can be further understood by reference to the followingexamples, which are provided by way of illustration and are not meant tobe limiting.

In the following examples, an embodiment referred to by the inventor asArmU has the following formulation. (The embodiment referred to as ArmUwas previously referred to by the inventor as N-hibit. All references toN-hibit in the Figures are references to ArmU.)

30% N-methyl-2-pyrrolidone (NMP)25% propylene glycol25% ethylene glycol15% N-(n-butyl) thiophosphoric triamide (NBPT)2.5% water2% TOPCITHIN™ sunflower lecithin2% TWEEN™ 20 polysorbate surfactant1% canola oil0.3% blue dye0.2% xanthan gum

The pH of the ArmU formulation used in the following examples was pH6.8. This formulation was found to be stable at room temperature for atleast 30 months with no precipitation of NBPT.

In the following examples, the ARBORITE™ and AGROTAIN™ productscontained approximately 24% NBPT by weight of solution. These knowncommercial products therefore contained approximately 60% greater theconcentration of NBPT compared to ArmU.

Experiment 1

Experiment 1 tested ammonia emissions from samples of urea granulescoated with ArmU, ARBORITE™ or AGROTAIN™. The control sample wasuncoated urea, and the three test samples were: (i) urea coated with 3L/1000 kg of ArmU, (ii) urea coated with 3 L/1000 kg of ARBORITE™, and(iii) urea coated with 3 L/1000 kg of AGROTAIN™. The samples were placedin clear plastic jars with lids. A hole was pierced in each lid for thepurpose of inserting an ammonia measuring tube into the jar, and anyopenings formed from the piercing around the tube were sealed with softclay. The results are shown in FIGS. 1A, 1B and 1C. Levels of emittedammonia were measured in parts per million (ppm) at 24 h, 48 h, 72 h, 96h and 120 h after treatment, as shown in FIG. 1A. Urea coated with ArmUshowed significantly lower levels of ammonia emitted compared to theuncoated control sample and the urea coated with ARBORITE™. Urea coatedwith ArmU showed similar if not slightly lower levels of ammonia emittedcompared to urea coated with AGROTAIN™. FIGS. 1B and 1C show the ratiosat 24 h, 48 h, 72 h, 96 h and 120 h, of ammonia emitted from urea coatedwith AGROTAIN™ and ARBORITE™, respectively, over ammonia emitted fromurea coated with ArmU, measured, expressed as percentages.

Experiment 2

Experiment 2 tested ammonia emissions from samples of urea granulescoated with ArmU at different application rates. The control sample wasuncoated urea, and the five test samples were ArmU applied to urea atthe following application rates: 1 L/1000 kg, 1.5 L/1000 kg, 2 L/1000kg, 2.5 L/1000 kg and 3 L/1000 kg. The samples were placed in clearplastic jars with lids. A hole was pierced in each lid for the purposeof inserting an ammonia measuring tube into the jar, and any openingsformed from the piercing around the tube were sealed with soft clay.FIGS. 2A, 2B and 2C display results at 24 h, 48 h and 72 h respectively.All five test samples showed significantly lower levels of ammoniaemitted compared to uncoated urea. Lower levels of ammonia were emittedfrom urea coated with 2 L/1000 kg, 2.5 L/1000 kg and 3 L/1000 kg of ArmUcompared to urea coated with 1 L/1000 kg and 1.5 L/1000 kg of ArmU.Ammonia volatilization levels did not change as the application rate ofArmU was increased from 2 L/1000 kg to 3 L/1000 kg across the threepoints.

Experiment 3

Experiment 3 tested ammonia emissions from samples of urea granulescoated with ArmU, ARBORITE™ or AGROTAIN™, and mixed with soil. The soilwas topsoil collected from a home garden. The topsoil was dried andsieved to remove rocks and other debris. The control sample was uncoatedurea, and the three test samples were (i) ArmU applied at 2 L/1000 kg,(ii) ARBORITE™ applied at 3 L/1000 kg and (iii) AGROTAIN™ applied at 3L/1000 kg. The samples were placed in clear plastic jars. 200 grams oftopsoil were then subsequently added into each jar, and the jars wereclosed with lids. A hole was pierced in each lid for inserting anammonia measuring tube into the jar, and any openings formed from thepiercing around the tube were sealed with soft clay. FIG. 3A shows theamounts of ammonia emitted at 24 h, 48 h, 72 h and 7 days aftertreatment. Coated urea showed significantly lower levels of ammoniaemitted compared to the control, and coated urea containing any of thethree compositions showed similar levels of ammonia emitted. FIG. 3Bshows the amounts of ammonia emitted at 14, 21 and 28 days aftertreatment. Urea coated with ArmU and AGROTAIN™ showed similar levels ofammonia emitted. Lower amounts of ammonia were emitted from urea coatedwith ArmU and AGROTAIN™ compared to urea coated with ARBORITE™.

Experiment 4

Experiment 4 tested ammonia emissions from samples of urea-ammoniumnitrate (UAN) solution (28-0-0) combined with ArmU, ARBORITE™ orAGROTAIN™ as an additive. The control sample was UAN with no additive,and the four test samples were UAN with 1 L/1000 L of ArmU, 1.5 L/1000 Lof ArmU, 1.5 L/1000 L of ARBORITE™ and 1.5 L/1000 L of AGROTAIN™. Thesamples were placed in clear plastic jars with lids. A hole was piercedin each lid for inserting an ammonia measuring tube into the jar, andany openings formed from the piercing around the tube were sealed withsoft clay. FIG. 4 shows ammonia emissions from the control and testsamples at 1, 2, 5, 7, and 10 days after treatment. UAN containing ArmUand AGROTAIN™ emitted similarly low levels of ammonia, and were lowerthan ammonia emissions from UAN containing ARBORITE™.

Experiment 5

Experiment 5 was a field trial that tested the mixability andflowability of urea granules coated with ArmU. The field trial wasconducted on a commercial scale, in Miniota, Manitoba, Canada. Thetemperature during the field trial was about −11° C. at a relativehumidity of about 78%. FIG. 5A shows a measuring container containingArmU. As can be seen, the composition had a uniform appearance withoutany precipitates even at −11° C. (the small white spheres visible arebubbles not precipitates). As shown in FIG. 5B, ArmU was poured onto amoving belt carrying urea granules at an application rate of 2 L/1000kg. The moving belt was set at a speed of 17 mph. The urea granules withArmU applied was transferred to a vertical screw blender, as shown inFIG. 5C. No buildup of dust was visible in the screw blender during andafter blending. After four minutes of blending, ArmU uniformly coatedthe urea, as shown in FIG. 5D. A fertilizer blend comprising sulfur,nitrogen, phosphate, and potash at a 90-30-30-25 was subsequently addedat a 2:1 ratio of fertilizer blend to coated urea granules, and thefinal fertilizer product is shown in FIG. 5E.

The fertilizer was then applied to a total of 205 acres of land at arate of 351 pounds per acre of land (therefore 117 pounds of coated ureaper acre of land) using an Ag Chem Air Assist Floater applicator. FIG.5F is a partial view of a transfer auger used to transfer the fertilizerto the applicator, after transferring 25 tonnes of the fertilizer. Ascan be seen, there was minimal to no buildup of dust on the auger. FIG.5G is a partial view of a component of the applicator that contacts thefertilizer, before the application of the fertilizer to the land. FIG.5H is a partial view the component of the applicator after applying thefertilizer to 100 acres of land. FIG. 5I is a partial view the componentof the applicator after applying the fertilizer to 200 acres of land.FIG. 5G to 5I show that the fertilizer created no build-up of dust onthe applicator component. The minimal to no buildup of dust shown inFIGS. 5C and 5F to 5I is in contrast to significantly greater dustbuildup on the mixing, transfer and applicator machinery whenfertilizers comprising commercially available NBPT formulations such asAGROTAIN™ and ARBORITE™ were used under similar conditions.

Experiment 6

Experiment 6 tested the viscosities of ArmU, AGROTAIN™ and ARBORITE™.Samples were analyzed for viscosity at 20° C. with a shear rate of 105s⁻¹ using a rheometer. The results are shown in Table 1 below. ArmU hassignificantly lower viscosity than AGROTAIN™ and ARBORITE™.

TABLE 1 Viscosity of ArmU and commercial NBPT formulations SampleViscosity (cP) ArmU 12.8 AGROTAIN 26.1 ARBORITE 86.7

Experiment 7

Experiment 7 tested the freezing points of ArmU, AGROTAIN™ andARBORITE™. Samples were analyzed cryostat methodologies well known inthe art. The results are shown in Table 2 below. ArmU has asignificantly lower freezing point than AGROTAIN™ and ARBORITE™.

TABLE 2 Freezing points of ArmU and commercial NBPT formulations SampleFreezing point (° C.) ArmU −66 AGROTAIN −43 ARBORITE −34

Experiment 8

Experiment 8 was a greenhouse study that tested ammonia volatilizationlosses from urea-based fertilizers coated with ArmU and two knowncommercial compositions as an urease inhibitor when applied to soilsurfaces. The study was conducted using Dezwood soil. Dezwood soil has aloamy texture (having a combination of roughly 51% sand, 29.4% silt and19.6% clay), electrical conductivity (1:2 of soil and water) ofapproximately 348 μS/cm, pH of approximately 6.6, field capacity ofabout 35%, organic carbon of approximately 4.0%, and available nitrogenof about 40.3 μg/g. The air temperature in the greenhouse was within arange of approximately 19.6 to 25.6° C., and was 29.4° C. on one studyday. The control sample was urea granules with no urease inhibitor(“UUR”), and the four test samples were: (i) ArmU applied at 2 L/1000 kgof urea (“UR+Arm2”), (ii) ArmU applied at 3 L/1000 kg of urea(“UR+Arm3”), (iii) commercial composition 1 applied at 2 L/1000 kg ofurea (“UR+CP1”), and (iv) commercial composition 2 applied at 2 L/1000kg of urea (“UR+CP2”). In this study, the percentage of NBPT in ArmU was18%, in commercial composition 1 was 30%, and in commercial composition2 was unknown.

Each sample was applied to the center of the surface of Dezwood soilsprovided within each polyvinyl chloride cylindrical chamber at a rate ofapproximately 100 kg N/ha. Four replicates of each sample were tested.Each chamber had dimensions of approximately 20 cm in height and 15 cmin diameter. The chamber was filled with up to 5 cm of Dezwood soil fromthe bottom end of the cylinder at a bulk density of about 1.1 g/cm⁻³.The soils within the chambers were wetted to 75% of field capacity 24hours before fertilization. Immediately after fertilization, upper andlower acid-soaked polyfoam discs were dimensioned to tightly fit insideeach cylinder. The upper and lower discs may comprise dimensions ofabout 2.5 cm thick and 16 cm diameter. The discs were prepared bywashing and wringing out twice with di-ionized water, twice with 0.001 MH₂SO₄, and twice with glycerol-phosphoric acid solution (by dissolving400 mL of 14.7 M H₃PO₄ and 500 mL of glycerol in de-ionized water tomake up to 10 L of solution). The upper disc was situated at about 2 cmbelow the top end of each chamber, for shielding the lower disc fromatmospheric ammonia contamination, and the lower disc was situated atabout 5 cm above the surface of the treated soils for trapping theammonia volatilized from the samples.

At 1, 2, 4, 7, 14, 21, and 28 days after fertilization, the discs wereremoved from each chamber and replaced with newly prepared discs asdiscussed above. The lower discs were each placed in a plastic freezerbag of known weight for transport into the laboratory and weighed tocalculate the amount of absorbing solution trapped in the discs. Thelower discs were then placed in jars containing 250 mL of 2 M KCl. Thejars were covered, shaken, and the discs were thoroughly immersed in theKCl solution for about 30 minutes to extract the trapped ammonia. Thesolution was then decanted into a vial and an aliquot of the solutionwas analyzed for ammonia concentration using a discrete analyzer, forexample, the AQ2 Discrete Analyzer (SEAL Analytical Inc.). Some samples,(e.g., samples taken on two and seven days after fertilization) wereanalyzed immediately after decantation while other samples (e.g.,samples taken on one and four days after fertilization) were stored ataround 4° C. until analysis. At 28 days after fertilization, soils fromeach chamber were thoroughly mixed and a soil sample from each chamberwas taken and analyzed for ammonium-nitrogen concentration andnitrite+nitrate-nitrogen concentration using the discrete analyzer.Ammonium-nitrogen and nitrite+nitrate-nitrogen were extracted from thesoils using 2 M KCl.

FIG. 6A shows the amount of daily ammonia volatilization losses over a28-day experimental period, measured at 1, 2, 4, 7, 14, 21, and 28 daysafter fertilization. Coated-urea fertilizer showed significantly lowerlevels of ammonia losses compared to the uncoated-urea fertilizer. Asshown in FIG. 6A, maximum ammonia volatilization loss from the controloccurs between two to four days after fertilization, with an emittedammonia level of around 16 kg N/ha. The test samples showed significantreduction in ammonia volatilization losses during this period.Coated-urea fertilizer containing any of the three compositions showedsimilar levels of ammonia losses. Similar levels of ammonia were emittedfrom urea fertilizer coated with 2 L/1000 kg or 3 L/1000 kg of ArmU,suggesting that ammonia volatilization levels did not change as theapplication rate of ArmU was increased from at least 2 L/1000 kg to 3L/1000 kg.

FIG. 6B is a table showing cumulative ammonia volatilization losses overa 28-day period, measured at 1, 2, 4, 7, 14, 21, and 28 days afterfertilization. The differences between the cumulative mean ammoniavolatilization losses between treatment groups were assessed by theTukey-Kramer Multiple Comparisons test, and the means were consideredstatistically different at a significance level of 5%. As shown in FIG.6(b), some values are followed by a letter (e.g., a or b). The valuesthat are followed by the same letter indicate that the values are notsignificantly different at a 5% significance level. All four testsamples showed significantly lower levels of cumulative ammonia losscompared to the control. Urea fertilizer coated with ArmU showed similarlevels of cumulative ammonia loss compared to the urea fertilizer coatedwith commercial compositions 1 and 2. In fact, urea fertilizer coatedwith 3 L/1000 kg of ArmU showed slightly lower levels of cumulativeammonia loss compared to the other test samples. FIG. 6C shows theratios of cumulative ammonia volatilization loss from coated-urea basedfertilizer over the cumulative ammonia volatilization loss from thecontrol at 28 days after fertilization, measured, expressed aspercentages. By 28 days after fertilization, the four test samples(coated-urea based fertilizer) emitted ammonia levels of approximately0.96-1.21 kg N/ha (as shown in FIG. 6B); this is a roughly 94-96% lowerammonium loss than the control (as shown in FIG. 6C).

1. A nitrogen stabilizing composition comprising: 10% to 18% w/wN-(n-butyl) thiophosphoric triamide (NBPT); a solvent comprisingN-methyl-2-pyrrolidone (NMP), and two or more of propylene glycol,ethylene glycol, morpholine and glycerine; a light oil; and anemulsifier.
 2. A composition according to claim 1 wherein the solventcomprises N-methyl-2-pyrrolidone (NMP), propylene glycol and ethyleneglycol.
 3. A composition according to claim 1 comprising 1% to 5% w/w ofthe light oil.
 4. A composition according to claim 3 wherein the lightoil is vegetable oil.
 5. A composition according to claim 1 comprising1% to 5% w/w of the emulsifier.
 6. A composition according to claim 5wherein the emulsifier is sunflower lecithin.
 7. A composition accordingto claim 1 further comprising 1% to 5% w/w of a surfactant.
 8. Acomposition according to claim 7 wherein the surfactant is polysorbate20.
 9. A composition according to claim 1 wherein the pH of thecomposition is pH 6.5 to 7.5.
 10. A composition according to claim 1comprising 10% to 15% NBPT.
 11. A composition according to claim 1wherein the composition is provided in a ready-to-use form or aconcentrated form.
 12. A composition according to claim 11 wherein theconcentrated form is selected from the group consisting of a liquid,gel, and reconstitutable powder.
 13. A composition according to claim 1wherein the composition is coated with a urea fertilizer to produce acoated urea fertilizer mixture.
 14. A composition according to claim 13wherein the urea fertilizer is granular.
 15. A composition according toclaim 13 wherein the urea fertilizer is in aqueous solution.
 16. Acomposition according to claim 15 wherein the aqueous solution is aurea-ammonium nitrate (UAN) solution (28-0-0).
 17. A compositionaccording to claim 13 wherein the composition is coated with the ureafertilizer at approximately 1 L/1000 kg to 10 L/1000 kg.
 18. Acomposition according to claim 17 wherein the composition is coated withthe urea fertilizer at a rate in a range of approximately 2 L/1000 kg to3 L/1000 kg.